diff --git a/picocli-codegen-tests-java9plus/src/test/java/picocli/annotation/processing/tests/Issue2430Test.java b/picocli-codegen-tests-java9plus/src/test/java/picocli/annotation/processing/tests/Issue2430Test.java
new file mode 100644
index 000000000..9bdc720bb
--- /dev/null
+++ b/picocli-codegen-tests-java9plus/src/test/java/picocli/annotation/processing/tests/Issue2430Test.java
@@ -0,0 +1,37 @@
+package picocli.annotation.processing.tests;
+
+import com.google.testing.compile.Compilation;
+import com.google.testing.compile.JavaFileObjects;
+import org.junit.Test;
+
+import javax.annotation.processing.Processor;
+
+import static com.google.testing.compile.CompilationSubject.assertThat;
+import static com.google.testing.compile.Compiler.javac;
+
+public class Issue2430Test
+{
+    @Test
+    public void testSpecInArgGroupClassUsedViaMixin() {
+        Processor processor = new AnnotatedCommandSourceGeneratorProcessor();
+        Compilation compilation =
+            javac()
+                .withProcessors(processor)
+                .compile(JavaFileObjects.forResource(
+                    "picocli/issue2430/Main.java"));
+
+        assertThat(compilation).succeeded();
+    }
+
+    @Test
+    public void testSpecInArgGroupClassUsedDirectlyInCommand() {
+        Processor processor = new AnnotatedCommandSourceGeneratorProcessor();
+        Compilation compilation =
+            javac()
+                .withProcessors(processor)
+                .compile(JavaFileObjects.forResource(
+                    "picocli/issue2430/SpecInArgGroup.java"));
+
+        assertThat(compilation).succeeded();
+    }
+}
diff --git a/picocli-codegen-tests-java9plus/src/test/resources/picocli/issue2430/Main.java b/picocli-codegen-tests-java9plus/src/test/resources/picocli/issue2430/Main.java
new file mode 100644
index 000000000..d13819cdd
--- /dev/null
+++ b/picocli-codegen-tests-java9plus/src/test/resources/picocli/issue2430/Main.java
@@ -0,0 +1,63 @@
+package picocli.issue2430;
+
+import picocli.CommandLine;
+import picocli.CommandLine.ArgGroup;
+import picocli.CommandLine.Command;
+import picocli.CommandLine.Mixin;
+import picocli.CommandLine.Model.CommandSpec;
+import picocli.CommandLine.Option;
+import picocli.CommandLine.ParameterException;
+import picocli.CommandLine.Spec;
+
+import java.util.concurrent.Callable;
+
+@Command(name = "main")
+class Main implements Callable<Integer> {
+
+    static class Options {
+        @Spec
+        CommandSpec spec;
+
+        int option1 = 1;
+        int option2 = 2;
+
+        @Option(names = "-o1")
+        void setOption1(int value) {
+            if (value > 10) {
+                throw new ParameterException(spec.commandLine(), "option1 must be <= 10");
+            }
+            this.option1 = value;
+        }
+
+        @Option(names = "-o2")
+        void setOption2(int value) {
+            if (value > 10) {
+                throw new ParameterException(spec.commandLine(), "option2 must be <= 10");
+            }
+            this.option2 = value;
+        }
+    }
+
+    static class SharedOptions {
+
+        @ArgGroup(exclusive = false, heading = "Shared options%n")
+        Options options = new Options();
+    }
+
+    @Mixin
+    SharedOptions sharedOptions = new SharedOptions();
+
+    @Override
+    public Integer call() throws Exception {
+        System.out.printf("Hello world: o1 = %s, o2 = %s%n",
+            sharedOptions.options.option1,
+            sharedOptions.options.option2
+        );
+        return 0;
+    }
+
+    public static void main(String[] args) {
+        int exitCode = new CommandLine(new Main()).execute(args);
+        System.exit(exitCode);
+    }
+}
diff --git a/picocli-codegen-tests-java9plus/src/test/resources/picocli/issue2430/SpecInArgGroup.java b/picocli-codegen-tests-java9plus/src/test/resources/picocli/issue2430/SpecInArgGroup.java
new file mode 100644
index 000000000..2bb215188
--- /dev/null
+++ b/picocli-codegen-tests-java9plus/src/test/resources/picocli/issue2430/SpecInArgGroup.java
@@ -0,0 +1,22 @@
+package picocli.issue2430;
+
+import picocli.CommandLine.ArgGroup;
+import picocli.CommandLine.Command;
+import picocli.CommandLine.Model.CommandSpec;
+import picocli.CommandLine.Option;
+import picocli.CommandLine.Spec;
+
+@Command(name = "spec-in-arggroup")
+class SpecInArgGroup {
+
+    static class Options {
+        @Spec
+        CommandSpec spec;
+
+        @Option(names = "-x")
+        int x;
+    }
+
+    @ArgGroup(exclusive = false)
+    Options options = new Options();
+}
diff --git a/picocli-codegen/src/main/java/picocli/codegen/annotation/processing/AbstractCommandSpecProcessor.java b/picocli-codegen/src/main/java/picocli/codegen/annotation/processing/AbstractCommandSpecProcessor.java
index b5b7576a2..e7fc22866 100644
--- a/picocli-codegen/src/main/java/picocli/codegen/annotation/processing/AbstractCommandSpecProcessor.java
+++ b/picocli-codegen/src/main/java/picocli/codegen/annotation/processing/AbstractCommandSpecProcessor.java
@@ -929,23 +929,9 @@ private void connectModel(AbstractCommandSpecProcessor proc) {
                     logger.fine("Adding " + entry + " to commandSpec " + commandSpec1);
                     commandSpec1.addSpecElement(entry.getValue());
                 } else {
-                    Element enclosingElement = entry.getKey().getEnclosingElement();
-                    if (enclosingElement.getKind() == ElementKind.CLASS || enclosingElement.getKind() == ENUM) {
-                        TypeMirror typeMirror = enclosingElement.asType();
-                        TypeElement typeElement = (TypeElement) ((DeclaredType) typeMirror).asElement();
-                        List<? extends TypeMirror> interfaces = typeElement.getInterfaces();
-                        boolean valid = false;
-                        for (TypeMirror interf : interfaces) {
-                            if (interf.toString().equals("picocli.CommandLine.IVersionProvider")) {
-                                valid = true;
-                            }
-                        }
-                        if (!valid) {
-                            proc.error(entry.getKey(), "@Spec must be enclosed in a @Command, or in a class that implements IVersionProvider but was %s: %s", entry.getKey().getEnclosingElement(), entry.getKey().getEnclosingElement().getSimpleName());
-                        }
-                    } else {
-                        proc.error(entry.getKey(), "@Spec must be enclosed in a @Command, but was %s: %s", entry.getKey().getEnclosingElement(), entry.getKey().getEnclosingElement().getSimpleName());
-                    }
+                    // #2430 @Spec is also valid outside a @Command, for example in ArgGroup classes
+                    // or in IVersionProvider implementations; picocli injects the CommandSpec at runtime
+                    logger.fine("Not adding " + entry + " to any commandSpec: enclosing element " + entry.getKey().getEnclosingElement() + " is not a @Command");
                 }
             }
             for (Map.Entry<Element, IAnnotatedElement> entry : parentCommandElements.entrySet()) {